Co-Ax (Frankford Arsenal / Forster) Vs RockChucker for 2021!

[INTJ]

I have the Coax and the Rock Chucker. I cannot argue the the test results on the RC because mine is also extremely precise and consistent year after year.

I only use the Coax for bullet seating. Honestly the only two reasons I like the Coax is because of quick die changes and the brilliant design of the S-jaws that work on just about every case I reload without having to swap them around or change out shell holders like I do with other presses.

But I would never say that the Coax is a better, more precise or more consistent press than my old Rock Chucker because it simply isn’t true.

Measuring runout is a moot point when comparing presses. Runout is a direct result of the quality of your dies and bullets, not much to do with the quality of your press. If you want to compare a measurement on presses then measure seating depths and case shoulder bump. Now granted you also have to account for shoulder bounce, especially if using cheap brass, and bullet ogive inconsistencies, but I guarantee you there isn’t a press out there that will beat the consistent stroke length that I get with my Rock Chucker. It’s not even worth measuring headspace on Lapua brass that is FL sized in my RC because it’s is so consistent that you’ll be overcome with extreme boredom seeing the same exact number pop up on the caliper every time.

You are correct that seating bullets isn't the measure of a press, it's consistency in sizing. The larger presses usually have less deflection and thus size more consistently.

However, I'll wager my Prazipress is more consistent than a Rockchuker. I have done a lot of comparing between my Co-Ax and my Prazipress but not against my Rockchucker Supreme. That's because I remember getting better results from the Co-Ax and only use the Rockchucker for extraneous press tasks now. If I didn't have them all packed away I'd do a test with all three.

 

[Mouse-Gunner]

My Co-Ax press has been in use so long that it actually says Bonanza on it. I have been impressed with the consistent quality of the ammunition I turn out on it. Two years ago I bought a Sinclair run out checker only to find the Co-Ax press turns such consistent ammunition that there was no real point in checking the completed rounds regularly.

One of the handiest features of this press is the spent primer catcher when full length sizing and de-priming. The primers never get loose and end up on the floor. It is far superior to the one on my RCBS. I have not closely examined the Frankford Arsenal press, but the pictures I have seen of it do not show a mechanism for catching spent primers.

Just my $0.02.

 

[Evan]

You are correct that seating bullets isn't the measure of a press, it's consistency in sizing. The larger presses usually have less deflection and thus size more consistently.

However, I'll wager my Prazipress is more consistent than a Rockchuker. I have done a lot of comparing between my Co-Ax and my Prazipress but not against my Rockchucker Supreme. That's because I remember getting better results from the Co-Ax and only use the Rockchucker for extraneous press tasks now. If I didn't have them all packed away I'd do a test with all three.

View attachment 1216186

That's the first time I've seen a Prazi next to the other presses. It's a big boy, isn't it!

 

[BigBlueandGoldie]

I think those Prazi's would sell like hot cakes here if they had an American distributor. Typical German quality throughout; elegant looking machines.

 

[Ledd Slinger]

You are correct that seating bullets isn't the measure of a press, it's consistency in sizing. The larger presses usually have less deflection and thus size more consistently.

However, I'll wager my Prazipress is more consistent than a Rockchuker. I have done a lot of comparing between my Co-Ax and my Prazipress but not against my Rockchucker Supreme. That's because I remember getting better results from the Co-Ax and only use the Rockchucker for extraneous press tasks now. If I didn't have them all packed away I'd do a test with all three.

View attachment 1216186

I don’t think anything can be “more” consistent than my Rock Chucker. Maybe AS consistent.

As I said before, I don’t even measure runout or headspacing anymore because it’s so boringly consistent. But just for fun, I ran 10 pieces of Lapua 300 Norma Mag Improved brass (35 deg shoulder) thru the RC with a custom Whidden FL bushing die. Shoulder bump is .002” from fired form. Pretty good amount of brass to be moving so there’s some stress in the press for sure. Lot more than say a 223, 308, or 6BR.

Anyhow, here’s my measurement results. I had one case that seemed to get bumped an extra half thou (.0005”) than the others. Can’t get any better than that.




If doing really big stuff and finding you are getting some slight deflection, which definitely could happen, RCBS also makes a “Rebel” press. It basically just a RockChucker on steroids. (RC on left, Rebel on right)

 

[INTJ]

I posted this on another thread but it fits here. What I am describing is my perceptions sizing and measuring 70-75 cases on the Prazipress and the CoAx as I load for a LR BR match. When I get settled in my new location I'll try to remember to to an actual test with the Prazipress, the Co-Ax, and the Rockchucker Supreme.

A big issue that I have seen is I can't really determine sizing consistency with only 10 cases. I find that I get very consistent sizing until get to 30-40ish cases sized. It's around then that I start seeing a little less consistency with whatever press I am using.

Also, there is likely a little bit of variation in the quality of RCBS presses, so I don't question that @Ledd Slinger probably has a very good one.

Here is the post form the other thread:

To me, the critical feature of a press is how consistently it sizes brass. In general, bigger heavier presses have less deflection and size more consistently. While my Co-Ax is great, it does have more deflection than my Prazipress. Pulling hard in the Co-Ax handle will size more than light pulling in the handle. I would use this to make sure all my BR cases are within .0005" in shoulder length--assuming I can really measure to a half thousandth with my Mitituyo digital.

I was asked about my Prazipress in a PM and here was part of my response which is applicable to this thread. My percentages are approximate as I didn't keep a log of the actual numbers.

Using the custom Whidden dies in the Co-Ax I would have cases size with the first stoke to within a half thousandth about 60% of the time. Probably 30% of the cases would come out a thousandth too long and maybe 10% would be two thousandths too long. The cases that are too long would need to be sized once or twice more to get them within spec. On rare occasion I would get a case too short by a thousandth--probably self induced by over lubing.

Using the custom Whidden dies in the German Prazipress, I estimate 85-90% of the cases size to within a half thousandth. The others are never more than one thousandth too long. I never get any too short unless I over lube them.

I also find that I get more consistency using RCBS case lube and a lube pad vs using Imperial with my fingers.

 

[Ledd Slinger]

I only use my coax for seating because it’s so easy to flick a different die in there and the S jaws work on all my cases from .378” 20 cal varmint to .532” magnum rims. I also just keep the short handle on it for a quick fast stroke on seating. Would need to change back to the longer handle for leverage on FL sizing. Definitely not as consistent with FL sizing as my RCBS so it never sees any sizing.

T7 has the most deflection of my presses. You can easily see the turret flex upward with your naked eye during FL sizing. But I still use it for FL sizing my varmint rounds because I don’t need crazy good consistency and it’s nice having a turret set up for multiple rounds. If a round shoots a little off due to inconsistent sizing and misses a ground squirrel at 300-500 yards, I really don’t care. Always plenty more varmints to shoot at.

My target rifles and big game hunting rifles all get FL sized on the Rock Chucker so they get the best consistency

 

[Murray Brook]

@INTJ
Any idea what could be happening after 30-40 cases to give less consistency.

 

[INTJ]

@INTJ
Any idea what could be happening after 30-40 cases to give less consistency.

I think it could only be that I am changing something in how I pull the handle or lubing cases.